A couple things come to mind for me regarding the light box lamps or whatever they are:
1) is it mainly to be a work of art that gets looked at, or is it to be a light source for the room? One possible vision is more like a luminous color accent along the lines of a neon bar light or something? But that would seek out less bare light leakage and all coming through your pics.
2) how much ambient illumination comes out of the opening at the top vs. what would come through the walls (picture part)?
The reason I was asking -- if it's possible to keep too much light from coming out the top, it could work nicely as a night light. And you could have nocturnal themes.
Ours has an opening at the top and sits on a table, and the effect of soft light is not as effective as it might be (we got one s a gift that had a leaf embedded in rice paper. Sort of a meditation thing, but it's too bright.
Other thought is that you could invert it perhaps have it hanging like a swag lamp over a table or pool table where you don't want the light shining in people's eyes from the side, but rather onto a surface. Think pool table tiffany style lamps that were really popular for a while. In that case, the pic you paint could be darker with deeper colors.
But the ratio of the amount of light coming through which part of the lamp would matter I think.
In this painting's case, this very light theme, as you have it, would indicate the purpose of it is for a good deal of illumination in every direction.
Very fun stuff. Hope this helps for approaches -- form follows function and all that happy design stuff.
I like your painting. Would be best though to see how the lumination and style and colors play in context.
"Not a bit is wasted and the best is yet to come. . ." -- remembered from a dream